A process of this type is described in BE-A-892 262 of Feb. 25, 1982 of the applicant. In this known process an agitator is found in the water tank, in its highest position. When this agitator experiences resistance from the ice that is formed in the tank, the motor of an agitator device will rotate in relation to the frame and this motor thereby turns an electrical switch which is part of organs which control the refrigeration mechanism and the aforementioned means.
The turning of this microswitch has as a consequence that means for opening and closing the water supply pipe open this pipe. Through the water supplied, the tank becomes heavy enough to move from its uppermost position to its lowest position. But before this tank has reached its lowest position, the protruding parts are heated by heating fluid so that the ice cubes come free from these protruding parts. The refrigeration mechanism no longer cools the protruding parts in the meantime.
The filled tank, in its lowest position, allows water to flow away through an opening. After sufficient water has flowed away through the opening, the tank with its contents will have become sufficiently light to rotate upwards again. During this upward movement the defrosting is terminated and cooling fluid is again sent through the evaporator. But before the tank has reached its uppermost position a small amount of water is again allowed into the tank, however, not sufficient to prevent the upward movement of the tank.
This known process is indeed very simple but still presents the risk that during the defrosting one or more ice cubes remain hanging on the protruding parts. Through the deposit of scale on the protruding parts they can become rough through which this risk increases. During the following cycle, when the tank is again situated at the top, and cooling occurs again the agitator in the tank will very quickly be slowed down by the cube that has remained hanging, even before sufficient ice is formed around the protruding parts. Cooling will therefore be stopped too early and the defrosting start too quickly. Larger and smaller ice cubes are obtained and through the decreased cooling cycle and therefore the frequent defrosting periods the production of ice is reduced.
The invention has the purpose of remedying these disadvantages and to provide a process for making ice cubes of the above mentioned type whereby the ice cubes have almost the same size and the reduction of the production of ice as a result of ice cubes which remain hanging on the protruding parts is avoided, regardless of the manner in which the thickness of the ice formed and therefore the stopping of the cooling and starting of the defrosting is determined.
For this purpose an upper grid hingedly mounted around a horizontal axis is pushed up, by the movement of the tank from said lowermost position to said uppermost position, into an uppermost position in which position it is located between the protruding parts so that, when the ice is formed around said parts the grid is retained by said ice and cannot go down as long a all ice has not fallen off, and in that the defrosting is only stopped and subsequently the refrigerating of the protruding parts restarted after said grid has hinged downwards from its uppermost position and thus after all the ice has fallen off.
The control that all ice cubes have fallen off is effected in a very simple mechanical manner. As long as all ice cubes have not fallen off, the new cycle for making ice cubes cannot start again and the defrosting continues. The duration of the defrosting can therefore be determined by the ice cubes falling off and therefore in a very simple and certain manner.
In a process for making ice cubes, the use of a feeler which detects whether an ice cube has fallen off the protruding parts of an evaporator is in itself already known from U.S. Pat. No. 3,418,823. In this known process the feeler is however in the shape of a finger which only controls one single ice cube and obviously does not offer the desired security that all ice cubes have fallen off. The ice cube is indeed controlled from which it is assumed that the latter will fall by roughening the protrusion around which this cube is formed but after a lapse of time the roughness of the other protrusion can become equally great, so that another cube may still remain hanging longer.
In an advantageous embodiment of the invention the water supplied for moving the tank from the uppermost position to its lowermost position is at the same time used for slightly defrosting the ice formed around said protruding parts.
Because absolute security is achieved as long as defrosting occurs until all ice formed around the protuding parts has fallen off and as long as this has not been effected the cycle cannot continue further, defrosting with cold water can be effected without problems and namely with the cold water that must be supplied to fill the water tank.
In the above mentioned known process warm gas is used for the defrosting, the temperature of which is controlled by a thermostat.
The invention also relates to an apparatus specifically designed for carrying out the above mentioned process.
The invention thus also relates to a device for making ice cubes which contains a frame, a refrigeration mechanism which in turn has a compressor, a condenser, an expansion element and an evaporator with downward directed protruding parts permanently mounted on this frame, means to slightly defrost the iced formed around the protruding parts and to cause it to fall off, a water tank that is movably mounted on the frame, a water supply pipe which exits above the tank, means to move the tank from an uppermost position around the above mentioned protruding parts to a lowest position and vice versa, which means comprise themselves to open and close the water supply pipe, and organs which controls the aforementioned refrigeration mechanism and the above mentioned means, characterized in that it contains an upper grid that is hingedly mounted around a horizontal axis to the frame and extends in the uppermost position of the tank on the top just between the downward directed protruding parts of the evaporator so that, when the ice cubes have been formed around these protruding parts it is situated above the ice cubes and cannot go down as long as all ice cubes have not fallen off, while the organs which control the refrigeration mechanism and the above mentioned means have at least one switch which is controlled by the upper grid.
In a particular embodiment of the invention the evaporator is of the type that has a number of fingers directed downwards of which the uppermost extremities, on the one hand, are mounted between two parts of the refrigeration pipe of the evaporator, and, on the other hand, are situated above these parts in a defrosting liquid supply.
In another particular embodiment of the invention the device has a storage tray for ice cubes which is situated under the water tank and a feeler grid that is mounted on top of the storage tray, while the organs which control the refrigeration mechanism and the above mentioned means have a switch which is controlled by this feeler grid to switch off at least the means for moving the tank when sufficient ice is present in the storage tray.